Small modular reactor design could be a 'SUPERSTAR'

February 10, 2012
By Louise Lerner

(PhysOrg.com) -- Though most of today's nuclear reactors are cooled by water, we've long known that there are alternatives; in fact, the world's first nuclear-powered electricity in 1951 came from a reactor cooled by sodium. Reactors cooled by liquid metals such as sodium or lead have a unique set of abilities that may again make them significant players in the nuclear industry.

At the U.S. Department of Energy's (DOE) Argonne National Laboratory, a team led by senior nuclear engineer James Sienicki has designed a new small reactor cooled by leadthe Sustainable Proliferation-resistance Enhanced Refined Secure Transportable Autonomous Reactor, or SUPERSTAR for short.

Small modular reactors, or SMRs, are small-scale nuclear plants that are designed to be factory-manufactured and shipped as modules to be assembled at a site. They can be designed to operate without refueling for 15 to 30 years. The concept offers promising answers to many questions about nuclear powerincluding proliferation, waste, safety and start-up costs.

SUPERSTAR is an example of a so-called "fast reactor," a type fundamentally different from the light-water reactors common today. Light-water reactors use water both as a coolant and as a moderator to slow down neutrons created in the fuel as it fissions. Instead, fast reactors use materials that don't slow down neutronsoften a liquid metal, such as sodium or lead.

Like all new generations of reactors, SUPERSTAR has "passive" safety systemsbackup safety measures that kick in automatically, without human intervention, in case of accidents. For example, all reactors have control rods incorporating substances that absorb neutrons and stop nuclear chain reactions. SUPERSTAR's rods can be suspended above the reactor core held in place by electricity. If the plant loses power, the control rods will automatically drop into the core and stop the reaction.

In addition, SUPERSTAR's lead coolant is circulated around the core by a process called natural circulation. While existing plants use electrically-driven pumps to keep the water moving, SUPERSTAR exploits a law of physics to move the coolant.

"In any closed loop, with heat at the bottom and cooling on top, a flow will develop, with the heated stream rising to the top and cooled stream going down," explained Anton Moisseytsev, an Argonne nuclear engineer also working on the reactor design. "The SUPERSTAR design takes advantage of this featureits lead coolant is circulated solely by natural circulation, with no pumps needed. And of course, having no pumps means no pump failures."

This means that if the plant loses power, as happened at the Fukushima Daiichi plant in Japan, the reactor does not need electricity to cool the core after shutdown.

Although the SMR concept has been around for decades, the idea has gained greater traction in recent years. Both President Obama and U.S. Department of Energy Secretary Steven Chu have extolled the virtues of SMRs; Secretary Chu said their development could give American manufacturers a "key competitive edge."

For example, the smaller size of SMRs gives them greater flexibility. "A small grid in a developing nation or a rural area may not need the 1,000 megawatts that a full-size reactor produces," Sienicki said. "In addition, SUPERSTAR can adjust its own power output according to demand from the grid."

Sienicki and his colleagues designed the reactor so that it could be shipped, disassembled, on a train. SMRs have been pinpointed for use in developing nations or outlying areas; these plants could be dropped off at a site and easily installed.

Because the plant runs for decades on a single installment of fueland operators need never directly interact with the fuel, which is sealed in the coreSMRs also address proliferation concerns. Reducing access to the fuel lowers all the risks associated with creating and changing fuel, such as uranium enrichment technology.

Finally, SMRs could also offer cost benefits. After major cost overruns on plants in the 1980s, investors have been wary of financing new nuclear plants. Small modular reactors reduce the risk in investing in new plants; the start-up cost would be less than those for full-size reactors. In addition, the parts for the reactors could be manufactured in assembly lines at factories, further diminishing the cost.

Several European countries have shown interest in lead-cooled reactors, Sienicki said. Studies such as Cinotti et. al ("The ELSY Project," International Conference on the Physics of Reactors, 2008) suggest that they may be cheaper to build than sodium-cooled reactors.

A paper, "An Improved Natural Circulation, Lead-Cooled, Small Modular Fast Reactor for International Deployment," was presented at the 2011 International Congress on Advances in Nuclear Power Plants. Argonne nuclear engineers Jim Sienicki and Anton Moisseytsev co-authored the paper, along with Argonne's Gerardo Aliberti, Sara Bortot at the Politecnico di Milano, Italy and Qiyue Lu at the University of Illinois at Urbana-Champaign.

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41 comments

Like all new generations of reactors, SUPERSTAR has "passive" safety systemsbackup safety measures that kick in automatically, without human intervention, in case of accidents. For example, all reactors have control rods incorporating substances that absorb neutrons and stop nuclear chain reactions

All other reactor types have that, too.

And of course, having no pumps means no pump failures

But it also means that you have an immediate meltdown in the event of a leak because you cannot augment the pump pressure to compensate. Although the mediator rods are there to prevent that - in past catastrophes temperatures have risen fast to the point where mediator rods have warped and were unable to be inserted. This design does not prevent such an accident type.

antialias...there are EM pumps that the reactors use that do not contain any moving parts. Also, fast reactors require reflector shields in order to operate. These shields also drop away in the event of a power failure. Fission then stops. So there are multiple avenues of safety protection with this type of reactor.

I would definitely want one in my back yard, assuming me and my ancestors (30-60 years of operation!) would get a cut of the profits.

Any reactor has multiple safety features, the above article mentioned one with a breif comment about others. It's an interesting concept I hope they can make it work. Being able to supply small communities,neighborhoods,or even individual structures this way,deserves further research.

If these things become household items in rural areas and developing nations: How exactly are they safe from being manipulated, opened up, sold to third parties, abused, ... ?

Right now we have nuclear materials in a few, well guarded areas. But spreading this stuff around the country and around third world nations doesn't exactly make me confident that this is somehow combatting proliferation or making waste management any better. Maybe I'm missing something here...

Do you really think they'd just be plopped down into some farmer's basement?

Well, the article talks about (and I quote):

A small grid in a developing nation or a rural area

Burying stuff does not make it immune to manipulation. And setting these up in developing nations does put it in the hand of rural governors. I'm not at all confident that politicians in the first world are immune to bribery and shady deals - much less those in developing nations.

And how exactly does this answer the question about waste (as claimed by the article)? Just leave it buried? the more I reread this article the more it sounds like a PR piece.

Proliferation resistance of these reactors stems from the fact that there is no need to refuel for 15-30 years, so the "customers" do not need to manipulate with fuel and waste. Those are the primary sources of radioactive material for terrorists, so the proliferation advantage is undeniable.

Since the reactors are smaller, there would be more of them, which could be seen as a proliferation disadvantage. On the other hand, there is no reason why many of these reactors could not be centralised in big multi-reactor power plants under tight supervision as in conventional plants.

And how exactly does this answer the question about waste (as claimed by the article)?

Those are the primary sources of radioactive material for terrorists, so the proliferation advantage is undeniable.

What would keep some terrorist group from taking over a village and unearthing the reactor? Developing nations and rural raeas aren't noted for being very stable. What do we do in the event a government breaks down (Somalia type scenario). How would the radioactive material be kept out of the hands of usurpers?And with these types of reactors you have to consider the entire reactor nuclear waste (and a lot of the gound it is buried in) so no advantage here.And if something DOES go wrong (as is inevitable if you deploy hundreds of these - one or two WILL have manufacturing faults) theyre underground. No chance to get at them quick for cleanup before the gunk seeps into the soil.

A couple thoughts: The use of lead or sodium is about trade-offs. Lead doesn't react with air and water, but does represent an environmental poisoning if leaks (though not high order poisoning.) Sodium can be cleaned with chlorine (bleach?) to turn it into table salt. And lead is *seriously* heavier than sodium, more than an order of magnitude. Sodium is lighter than aluminum, which makes wear and tear on cooling systems far less and reduces costs making it safe against seismic events (earthquakes).

As for tampering, yea, if these are everywhere, somebody is going to get it in their head to try and blow it up, or get inside. However something filled with liquid sodium might present a formidable barrier to getting inside. Though it would make a terrific media moment if blown up!

Water cooled are the only types I've had any experience with. Does anyone know what happens to the lead coolant should the core overheat & head to "meltdown"? Does the lead coolant encase the core after falling below melting temperature & how long would that take (you certainly want it to occur in a very short time)?

Do you really think they'd just be plopped down into some farmer's basement?

Well, the article talks about (and I quote):

A small grid in a developing nation or a rural area

Burying stuff does not make it immune to manipulation. And setting these up in developing nations does put it in the hand of rural governors. I'm not at all confident that politicians in the first world are immune to bribery and shady deals - much less those in developing nations.

And how exactly does this answer the question about waste (as claimed by the article)? Just leave it buried? the more I reread this article the more it sounds like a PR piece.

The only reason there is a nuclear waste problem is because of US policy to not recycle nuclear fuel. Only very small masses of radioactive waste are generated, but it is spread throughout all the unspent fuel. If we separated the remaining fuel from the waste there would not be significant amounts of waste. That's what I heard...

Natural circulation in a lead-coolant reactor precludes any possibility of over-heating and meltdown. The coolant continues to circulate until the core drops below the melting point of lead. Since that is much lower than the melting point of the fuel, encasement is guarantied.

This design has been around a long time. The USSR Lira-class submarines were constructed in the early '70s using the technology. Unfortunately, they chose to design for highest power density rather than long-life to minimize the reactor's size. This meant frequent replacements of the core were necessary.

It's nice - but will buy it, when cold fusion reactors will become available and complete safe http://www.e-catw...emitted/ We can even expect, nuclear reactors will be embargoed after then just with respect to their risk of misuses with various terrorist groups.

Natural circulation in a lead-coolant reactor precludes any possibility of over-heating and meltdown. The coolant continues to circulate until the core drops below the melting point of lead. But how much time does this require was the crux of my question....?

This design has been around a long time. The USSR Lira-class submarines were constructed in the early '70s using the technology. Unfortunately, they chose to design for highest power density rather than long-life to minimize the reactor's size. This meant frequent replacements of the core were necessary.

And I think these were sodium cooled. So far as I've heard the US Navy only built one sodium cooled reactor in a sub, and soon after commissioning leakage developed in the hot leg heat exchanger causing tiny amounts of sodium to be caught up into the high pressure steam supply leading to the high pressure turbine, this shortened the life of the turbine blades as well as posing a slight radiation hazard.

cant see the down side with these proliferating around a far flung lightly populated country like Australia. If the anti-nuke brigade can be countered by the engineered safe guards this can kill a lot of coal fired plants in my country. Back to the future indeed.

Do these fast reactors (that don't slow neutrons) still require reactor grade uranium or can more stable (and more readily available) isotopes be used as the reactor fuel?

How reactive does the fuel have to be? Will U-238 work?

The uranium has to be enriched somewhat for fast neutron reactors, but much less than for slow neutron ones. There is some Plutonium enrichment but not a tremendous amount, because the U-238 absorbs neutrons and is converted to U-239, which then decays in 2 steps into Plutonium-239. This process is quite fast. Then the Plutonium fission's and is the primary producer of heat and power. You just need enough U-235 to supply enough fast neutrons to get the ball rolling. This is why these reactors are much less of a proliferation threat. They don't contain material you can make a bomb out of.

What would keep some terrorist group from taking over a village and unearthing the reactor? Developing nations and rural raeas aren't noted for being very stable. What do we do in the event a government breaks down (Somalia type scenario). How would the radioactive material be kept out of the hands of usurpers?And with these types of reactors you have to consider the entire reactor nuclear waste (and a lot of the gound it is buried in) so no advantage here.And if something DOES go wrong (as is inevitable if you deploy hundreds of these - one or two WILL have manufacturing faults) theyre underground. No chance to get at them quick for cleanup before the gunk seeps into the soil.

This thing hasn't been thought through at all.

not any more dangerouse than Russia " Lossing " nuclear material regually. Have to say we do need new sources of energy such as this as dreams such as renewables Fusion etc are many years away.

cant see the down side with these proliferating around a far flung lightly populated country like Australia. If the anti-nuke brigade can be countered by the engineered safe guards this can kill a lot of coal fired plants in my country. Back to the future indeed.

The anti-nuke brigade is by definition "anti" nuke. The greenies will oppose any form of development like coal plants, even wind power , but when it comes to nuclear power something churns up deep inside their selves and all of a sudden coal plants are OK as long as you don't make nuclear plants.

Who cares if modern plants actually produce WAY less radiation than even a medium sized coal plant. "NUKES ARE BAD" , period.

not any more dangerouse than Russia " Lossing " nuclear material regually.

Exactly. If a country with a huge security apparatus and government control over nuclear facilities/weapons can't manage it I'm not confident that rural areas and developing nations can.

They don't contain material you can make a bomb out of.

Ever heard of a dirty bomb? That's much more likely than anyone actually detonating a nuke. And the material in this reactors is perfectly fine for a dirty bomb.

It is far easier to blow up oil refineries than to mess with molten lead . These new reactors are inherently safer since they are sealed shut and designed to operate without opening for decades , a LOT more difficult to ferret out U-235 out of these.

and all of a sudden coal plants are OK as long as you don't make nuclear plants.

I really don't know why this lie keeps getting rehashed so often. I am pretty gree - and I know a lot of people who are. But I have yet to meet any eco-minded person who will say that coal is an OK replacement or stand-in for nuclear.

The world isn't simple black and white. It's not "if you are against nuclear you have to be for coal". To make that inferrence is just stupid.

cant see the down side with these proliferating around a far flung lightly populated country like Australia. If the anti-nuke brigade can be countered by the engineered safe guards this can kill a lot of coal fired plants in my country. Back to the future indeed.

The anti-nuke brigade is by definition "anti" nuke. The greenies will oppose any form of development like coal plants, even wind power , but when it comes to nuclear power something churns up deep inside their selves and all of a sudden coal plants are OK as long as you don't make nuclear plants.

Who cares if modern plants actually produce WAY less radiation than even a medium sized coal plant. "NUKES ARE BAD" , period.

The world isn't simple black and white. It's not "if you are against nuclear you have to be for coal".

It is in fact quite black and white in reality. To think that we can get rid of both fossil fuels and nuclear, and meet the energy needs of the world with renewables is a completely absurd proposition in foreseeable future. So it is either fossil fuels, or nuclear.

If the green movement was pro-nuclear (as it should be) instead of knee-jerk antinuclear pseudogreen movement we got, then humanity may already have been A LOT further in our fight against fossil fuels.

Theoretically you are right, but in reality either you are pro-nuclear, or you are not really "green" or "sustainable".

The only green technology in this moment is a cold fusion. Renewable technologies are very material hungry - for example the wind plants introduced a deficit of rare earth magnets, solar cells require indium and their rentability is disputable at the most areas on the world. The uranium simply cannot cover current energy demands and thorium is unfissile. http://lasttechag...-the-job The only way how to solve energetic crisis is to invest into cold fusion research, there is no other way around.

The only thing holding this back is a conspiracy by the big oil & coal companies to prevent construction of this perpetual motion machine, they buy up all the patents as fast as they are granted, therefore we will never reap its' benefits (or do I simply misunderstand the "fusion process" here).

The only thing holding this back is a conspiracy by the big oil & coal companies

This conspiratorial twaddling is just demagogic fog, trying to cover before publicity the fact, most of scientists are involved in research of alternative methods of energy production, conversion, transport and storage so they all participate on the ignorance of the cold fusion heartily as a single man.

Not true for breeder reactors.

Breeder reactors are even much more dangerous than the classical ones. Actually it's already much more perspective to research cold fusion, than the thorium fission with respect to present state of research of both. http://www.ieer.o...heet.pdf

The only thing holding this back is a conspiracy by the big oil & coal companies

This conspiratorial twaddling is just demagogic fog,

No, Cal. It's just that there are many of us here at this forum who are tired of your theories in "perpetual motion". The AWT stuff, Cold Fusion, etc., none of which is scientifically demonstrable. You have never had college courses in thermodynamics, and like Ethelred before you, the more you write the greater you demonstrate your incompetence to function in a science based environment.

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